BP oil spill a disaster without end for wildlife

Hundreds of beached dolphin carcasses, shrimp with no eyes, contaminated fish, ancient corals caked in oil and some seriously unwell people are among the legacies that scientists are still uncovering in the wake of BP's Deepwater Horizon spill in the US.

This week it will be three years since the first of 4.9 billion barrels of crude oil gushed into the Gulf of Mexico, in what is now considered the largest marine oil spill in the history of the petroleum industry.

As the scale of the ecological disaster keeps unfolding, BP is appearing daily in a New Orleans federal court to battle over the extent of compensation it owes to the region.

Infant dolphins have been found dead at six times average rates in January and February. More than 650 dolphins have been found beached in the oil spill area since the disaster began, more than four times the historical average.

Sea turtles were also affected, more than 1700 found stranded from May 2010 to November 2012 the last date for which information is available. The average number stranded annually in the region is 240.

Contact with oil may also have reduced the number of juvenile bluefin tuna produced in 2010 by 20 per cent, with a potential reduction in future of about 4 per cent.

Contamination of smaller fish also means toxic chemicals could make their way up the food chain after scientists found the spill had affected the cellular function of killifish, a common bait fish at the base of the food chain.

Deep sea coral, some of it thousands of years old, has been found coated in oil after the dispersed droplets settled on the sea bottom. A recent laboratory study found the mixture of oil and dispersant affected the ability of some coral species to build new parts of a reef.

Doug Inkley, a senior scientist for the US National Wildlife Federation and author of a report published this week, said: "These ongoing deaths particularly in an apex predator such as the dolphin are a strong indication there is something amiss with the Gulf ecosystem."

Scientists believe the 6.8 million litres of dispersant, sprayed as part of the clean-up, have cemented the disaster's toxic effect on ocean life and human health. The chemical, called Corexit, caused what some scientists have described as "a giant black snowstorm" of tiny oil globules, which has been carried around the ocean in plumes and has now settled on the sea floor. A November study found the dispersant to be 52 times more toxic than the oil itself.

Scientists believe the addition of dispersants made the oil more easily absorbed through the gills of fish into the bloodstream. Toxicologist Dr William Sawyer has studied concentrations of petroleum hydrocarbon in edible fish and shellfish in the region. Samples before the spill had no measurable PHC, whereas fish tested in recent months show tissue concentrations as high as 10,000 parts per million, or 1 per cent of all tissue. He said: "The study shows that the absorption [of the oil] was enhanced by the Corexit."

BP says the dispersants it used are "government approved and safe when used appropriately", and that extensive testing has shown seafood in the Gulf states is safe to eat.

Louisiana State University's Department of Oceanography and Coastal Sciences has found sea life in the Gulf with lesions and deformities it believes may be linked to the use of dispersants. These include shrimp and crabs missing eyes and claws. . BP claims these abnormalities are "common in marine life", had been seen in the region before, and are caused by bacterial infections or parasites.

It's not just wildlife that scientists believe has been affected. Louisiana doctor Michael Robichaux has documented 113 patients who he thinks were made ill by exposure to chemicals associated with the spill. Their most common symptoms include headaches, memory loss, fatigue, irritability, vertigo, nausea, blurred vision and insomnia.